Dynamic Seal

ABSTRACT

A dynamic shaft seal assembly is provided including a dynamic seal for engaging a rotary shaft. The dynamic seal includes a base portion that is mounted within a casing and has an axially extending barrel portion extending from a radially inner end of the base portion. The axially extending barrel portion terminates in a radially extending leg portion which extends inwardly from an end of the axially extending portion. A generally conically shaped seal portion extends from an end of the radially extending portion and the seal portion includes a radially inner face engaging the shaft and a radially outer face having a stiffening bead integrally formed thereon. The stiffening bead reduces the seal&#39;s propensity for “bell mouthing” while the axially extending barrel portion provides improved shaft followability for the dynamic seal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/048,745, filed Mar. 14, 2008, which is a divisional of Ser. No.11/285,652, filed Nov. 22, 2005, which is a continuation-in-part of U.S.patent application Ser. No. 11/065,023, filed on Feb. 24, 2005, thedisclosures of which are incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

The present invention relates to “lay-down” dynamic shaft seals, andmore particularly, to a dynamic shaft seal design to reduce the seal'storque, propensity for bell mouthing, and for providing improved shaftfollowability and improved ability to withstand internal excessivepressure or vacuum. The “lay-down” seal for their function rely onhydrodynamic pumping features as opposed to “standard” or“point-contact” seals that rely primarily on the intrinsic ability ofsome elastomers to pump in properly designed seals.

BACKGROUND AND SUMMARY OF THE INVENTION

Rotary shaft seals have been utilized in machinery, the automobileindustry, as well as other industries. Three major problems associatedwith seals designed to have substantial contact areas between the shaftand the lip of the seal are “bell mouth,” the shaft followability at lowtemperatures, and oil carbonization in the pumping grooves due to localtemperature rise causing increased torque. “Bell mouth” is a phenomenonassociated with the lift of the edge of the lip from the shaft. Theproblem is extenuated for highly incompressible materials, like rubberand PTFE. The ability of the seal to follow the shaft when the shafteither wobbles or is misaligned is also important to a seal design.

The present invention is designed to reduce seal torque, the propensityfor “bell mouthing” and also provides for improved shaft followabilityat low temperatures. The dynamic seal includes an annular mountingportion which is capable of being mounted to a casing which surrounds arotary shaft. The seal includes an axially extending portion extendingfrom the radially inner end of the mounting portion, with a radiallyextending portion extending inwardly from an end of the axiallyextending portion. A generally conically shaped seal portion extendsfrom an end of the radially extending portion with the seal portionincluding a radially inner face provided with a plurality of grooves orribs and a radially outer face having a special bead defining a regionof increased thickness. The bead acts as an integral spring to controlthe gap between the essentially conical portion of the seal and theshaft as well as a means for counteracting the “bell mouthing”propensity of the seal portion. The bead can have different shapesincluding a triangular-cross section or a rounded bead, as well as otherconfigurations which are deemed to be appropriate. The bead ispositioned slightly away from the edge of the lip to provide asufficient lip “lay-down” to properly engage the hydrodynamic pumpingfeatures, which would normally be located on the lip contact are betweenthe edge of the seal and the bead. The flexibility of the axiallyextending portion of the seal provides an improvement in the shaftfollowability due to the generally cylindrical shape of the axiallyextending portion having lower bending stiffness. Therefore, if thematerial of the seal does not have sufficient intrinsic elasticity,making the axially extending portion of the seal in a generallycylindrical shape improves the overall shaft followability. The lengthand the wall thickness of the cylindrical portion allow one to controlthe degree of flexibility to match the application requirements.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a detailed cross-sectional view of the dynamic seal accordingto the principles of the present invention;

FIG. 2 is a cross-sectional view of the dynamic seal disposed against ashaft according to the principles of the present invention;

FIG. 3 is a perspective view of the dynamic seal according to theprinciples of the present invention;

FIG. 4 is a cross-sectional view of second embodiment of the dynamicseal according to the principles of the present invention;

FIG. 5 is a cross-sectional view of the seal of FIG. 4 shown underinternal pressure;

FIG. 6 is a cross-sectional view of the seal of FIG. 4 shown undervacuum;

FIG. 7 is a cross-sectional view of a dynamic seal according to theprinciples of the present invention, incorporating a deflection limitingretainer;

FIG. 8 is a cross-sectional view of a dynamic seal according to theprinciples of the present invention including an interior shaft ring;

FIG. 9 is a cross-sectional view of a dynamic seal according to theprinciples of the present invention including a dust lip integrallyformed therewith;

FIG. 10 is a cross-sectional view of a dynamic seal according to theprinciples of the present invention, including a support ring andcasing;

FIG. 11 is a detailed cross-sectional view of the dynamic seal accordingto the principles of the present invention with a support ring disposedtherein; and

FIG. 12 is a cross-sectional view of the dynamic seal disposed against ashaft according to the principles of the present invention with asupport ring disposed therein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

With reference to FIGS. 1-3, the dynamic seal 10, according to theprinciples of the present invention, will now be described. The dynamicseal 10 is mounted to a casing 12 which is disposed in a fixed housing16 (best shown in FIG. 2) in a manner which is well known in the art.The dynamic seal 10 engages a rotary shaft 14 so that the dynamic seal10 provides a sealed relationship between the rotary shaft 14 and thehousing 16 in which the casing 12 is disposed. With reference to FIG. 1,the dynamic seal 10 includes a mounting portion 20 which is designed tobe engaged between first and second portions 12A, 12B of casing 12. Itshould be noted that the mounting portion 20 can take on many shapes andforms and is not considered to be particularly relevant to the presentinvention. The mounting portion 20 is mounted to the casing 12 which canbe made of plastic or metal and the mounting portion 20 can be clampedor bonded thereto according to well known mounting techniques.

The dynamic seal 10 includes an axially extending barrel portion 22extending from a radially inner end 20A of the mounting portion 20. Theaxially extending barrel portion 22 is preferably generally cylindricalin shape although other shapes, such as conical or a convoluted curveshape, can also be utilized. The dynamic seal 10 includes a radiallyextending portion 24 extending inwardly from a distal end 22B of theaxially extending barrel portion 22. A generally conically shaped sealportion 26 extends from a radially innermost end 24A of the radiallyextending portion 24. The seal portion 26 includes a radially inner face28 which may be provided with a plurality of grooves 30. The grooves 30can be helical in shape or can take other known forms. The grooves 30provided in the radially inner surface 28 of the seal portion 26 arecapable of retaining oil therein in order to provide lubrication betweenthe dynamic shaft seal 10 and rotary shaft 14 and also can provide apumping function for returning leaked oil to the oil side of the seal. Aradially outer face 32 of the conically shaped seal portion 26 isprovided with a stiffening bead 34 defining a region of increasedthickness. The stiffening bead 34 can have different shapes, including atriangular shape, as shown, or can have rounded or other shapeconfigurations. The stiffening bead 34 is positioned slightly away fromthe end edge 26A of the lip 26 to allow a proper contact area todevelop. The bead 34 serves as an integrally formed spring for biasingthe sealing lip 26 against the rotary shaft 14 for counteracting bellmouthing of the sealing lip 26. Normally, the seal lip-free edge facesthe oil side. However, reverse mounting is also possible. In that case,the design of the spiral grooves have to be accommodated appropriatelyto pump in the direction of the oil sump.

The improvement in the shaft followability of the dynamic seal 10 isprovided by the axially extending barrel portion 22. The generallycylindrical shape of the barrel portion 22 has a lower bending stiffnessthan other structures; therefore, the axially extending barrel portion22 is able to readily account for a wobbling shaft or a shaft that isout of center relative to the housing 16.

It should be noted that if desired or advantageous in a particularapplication, the dynamic shaft seal 10 of the present invention canoptionally include one or more axial or radial dirt protective lips 38as are known in the art, one of which is shown, for example, in FIG. 2.The optional dirt protective lip 38 can be formed integrally with thedynamic shaft seal, or can be formed separately therefrom and attachedthereto, and can have any of a number of shapes or configurations, as isalso known in the art. In addition, the lip 38 can protrude transverselyfrom the dynamic shaft seal in any of a number of directions, including,but not limited to, the exemplary angular relationship protrudinggenerally radially away and axially away from the shaft-engaging sealingcomponents, as shown, for example, in FIG. 2.

The radially extending leg portion 24 can be straight, as shown, oralternatively, can be provided with a convoluted shape. The outerdiameter of the shaft is specifically designed to have a larger diameterthan the inner diameter of the radially inwardly extending leg portion24. As illustrated in FIG. 2, the generally conically shaped sealportion 26 is designed to take on a generally cylindrical form whendeformed by the rotary shaft 14 and the leg 24 is designed to applypressure to the heel portion 36 of the seal portion 26. The leg portion24 acts radially on the end 22A of the barrel portion 22 which has alength sufficient to allow the barrel portion 22 to flex radiallyinwardly and outwardly to accommodate for shaft wobble or shaftmisalignment. The length of the leg portion is derivative from thelength of the seal portion, the amount of the seal-to-shaftinterference, and the distance between the casing and the shaft.

The dynamic shaft seal 10 of the present invention can be utilized forisolating an oil environment from an air environment disposed on eitherside of the dynamic seal 10. In order to optimize the seal design, thelength of the seal portion 26 and the stiffness of the bead 34(geometry, thickness, material, etc.) are specifically chosen forparticular applications. Furthermore, the thickness of the radiallyextending leg portion 24 is also specifically designed to providesufficient pressure on the heel 36 of the seal portion 26. The thicknessand length of the barrel portion 22 should also be specifically designedto accommodate the requisite flexibility of a particular application.The seal material composition for the dynamic seal can include plastic,rubber, or any of a wide variety of known elastomers, such as PTFE, TPE(thermoplastic elastomers), TPV (thermoplastic vulcanizates), andFlouroprene™ material, a composition described in U.S. Pat. No.6,806,306. An additional embedded spring in the bead may be utilized inorder to extend the life of the seal due to the fact that creep canoccur in thermoplastic or elastomeric materials which prevents thematerial from regaining its original properties. The spring would thenprovide an additional radial load on the seal surface that thethermoplastic material is incapable of maintaining over a long life. Thespring can also improve the robustness of the seal required incontaminated environments. Instead of imbedding, the spring can beplaced in a specially designed and manufactured spring groove aftercompletion of the molding operation (as is normal with other radial lipseals).

With reference to FIGS. 4-6, a dynamic seal according to a secondembodiment of the present invention will now be described. The dynamicseal 100 includes a mounting portion 102 which is designed to be engagedbetween first and second portions of a casing. It should be noted thatthe mounting portion 102 can take on many shapes and forms and is notconsidered to be particularly relevant to the present invention. Themounting portion 102 is mounted to a casing which can be made of plasticor metal and the mounting portion 102 can be clamped, bonded orotherwise secured thereto according to well-known mounting techniques.

The dynamic seal 100 includes an axially extending barrel portion 104extending from a radially inner end 102A of the mounting portion 102.The axially extending barrel portion 104 is preferably generallycylinder shaped although other shapes, such as conical or a convolutedcurve shape, can also be utilized. The dynamic seal 100 includes aradially extending portion 106 extending inwardly from a distal end 104Aof the axially extending barrel portion 104. A generally conicallyshaped seal portion 108 extends from a radially innermost end 106A ofthe radially extending portion 106.

The axially extending barrel portion 104 extends in a first axialdirection from mounting portion 102, while the generally conicallyshaped seal portion 108 extends from the radially innermost end 106A ofradially extending portion 106 in an axial direction opposite to thefirst axial direction.

The seal portion 108 includes a radially inner face 110 which may beprovided with at least one groove or a plurality of grooves. The groovescan be helical in shape or can take other known forms. The groovesprovided in the radially inner surface 110 of the seal portion 108 arecapable of retaining oil therein in order to provide lubrication betweenthe dynamic shaft seal 100 and rotary shaft 14 and also can provide apumping function for returning leaked oil to the oil side of the seal.

A radially outer face 112 of the conically shaped seal portion 108 isprovided with a stiffening bead 114 defining a region of increasedthickness. The stiffening bead 114 can have different shapes, includinga triangular shape as shown, or can have rounded or other shapedconfigurations. The stiffening bead 114 is positioned slightly away fromthe end edge 108A of the lip 108 to allow a proper contact area todevelop. The bead 114 serves as an integrally formed spring for biasingthe sealing lip 108 against the rotary shaft 114 for counteracting bellmounting of the sealing lip 108. The location and shape of the bead 114is dependent upon the specific application and the desired spring force.

Normally, the seal lip-free edge 108A faces the oil side. However,reverse mounting is also possible. In that case, the design of thespiral grooves has to be accommodated appropriately to pump in thedirection of the oil side.

With the design of the present invention, the dynamic seal 100 iscapable of withstanding excessive internal pressure or vacuum. FIG. 5illustrates a cross-sectional view of the dynamic seal 100 disposedagainst a shaft 14 and under a pressure of 170 MBAR. FIG. 6 illustratesthe dynamic seal 100 disposed against a shaft 14 and exposed to a vacuumpressure of −50 MBAR. In the case of excessive internal pressure beingapplied to the dynamic seal 100, the axially extending barrel portion 22which radially overlaps the seal portion 108 provides a radial springacting upon the radially extending portion 106 to limit the deformationin the seal portion 108.

In the case of an excessive vacuum being applied, the axially extendingbarrel portion 104 limits the axial movement of radially extendingportion 106, thus limiting the axial movement of the seal portion 108.

The improvement in the shaft followability of the dynamic seal 100 isprovided by the axially extending barrel portion 104. The generallycylindrical shape of the barrel portion 104 has a lower bendingstiffness than other structures. Therefore, the axially extending barrelportion 104 is able to readily account for a wobbling shaft or a shaftthat is out of center relative to the housing.

It should be noted that if desired or advantageous in a particularapplication, the dynamic seal shaft 100 of the present invention canoptionally include one or more axial or radial dirt protective lips 120as illustrated in FIG. 9. The optional dirt protective lip 120 can beformed integrally with the dynamic shaft seal, or it can be formedseparately therefrom and attached thereto and can have any of a numberof shapes or configurations, as is also known in the art. The radiallyextending leg portion 106 can be straight, as shown, or alternatively,can be provided with an angled or convoluted shape. As illustrated inFIGS. 5 and 6, the generally conically shaped seal portion 108 isdesigned to take on a generally cylindrical form when deformed by therotary shaft 14 and the leg 106 is designed to apply pressure to theheel portion of the seal portion 108. The leg portion 106 acts radiallyon the end 104A of the barrel portion 104 which has a length sufficientto allow the barrel portion 104 to flex radially inwardly and outwardlyto accommodate for shaft wobble or shaft misalignment. The length of theleg portion 106 is derivative from the length of the seal portion 108,the amount of the seal-to-shaft interference, and the distance betweenthe casing and the shaft.

The dynamic shaft seal 100 can be utilized for isolating an oilenvironment from an air environment disposed on either side of thedynamic seal 100. In order to optimize the seal design, the length ofthe seal portion 108 and the stiffness of the bead 114 (geometry,thickness, material, etc.) are specifically chosen for particularapplications. Furthermore, the thickness of the radially extending legportion 106 is also specifically designed to provide sufficient pressureon the heel of the seal portion 108. The thickness and length of thebarrel portion 104 should also be specifically designed to accommodatethe requisite flexibility of a particular application. The seal materialcomposition for the dynamic seal can include plastic, rubber, or any ofa variety of known elastomers, such as PTFE, TPE (thermoplasticelastomers), TPV (thermoplastic vulcanizates) and Flouroprene™ material.

With reference to FIG. 7, the dynamic seal 100 according to theprinciples of the present invention is shown mounted to a retainer ring130. The retainer ring 130 is designed to be press fit within a bore ofa housing and includes an axially extending portion 130A, a firstradially extending mounting portion 130B to which the dynamic seal 100is mounted, and a retaining flange 130C disposed at an opposite end ofthe axially extending portion 130A. A support ring 132 includes anaxially extending arm portion 132A and a radially inwardly extending armportion 132B. The axially extending arm portion 132A is designed to beretained by the retainer 130 and can include an inwardly angled exteriorsurface 134 which facilitates the support ring 132 to being press fitwithin retaining flange 130C. The radially inwardly extending armportion 132B is disposed adjacent to the radially extending portion 106of dynamic seal 100 with an axial gap extending therebetween. The gap136 permits axial movement of the radially extending portion 106, butlimits the axial movement thereof relative to the mounting portion 102.

With reference to FIG. 8, a dynamic seal 100, according to theprinciples of the present invention is shown utilized in a cassette-typeseal including a running sleeve 150 adapted to be mounted to a shaft andto be rotated therewith. The running sleeve 150 includes a finishedexterior surface 152 that is engaged by the seal portion 108 of dynamicseal 100. The running sleeve 150 also includes a radial wall portion150A extending adjacent to the radially extending portion 106 of thedynamic seal 100. The radial wall portion 150A limits the axial movementof the radially extending portion 106 of dynamic seal 100 in therightward direction as illustrated in FIG. 8. The radially extendingportion 106 of the dynamic seal 100 may also include a protrudingportion 154 that can come in contact with the radially extending wallportion 150A of running sleeve 150. The protruding portion 154 limitsthe contact surface that engages the radial wall portion 150A so as tolimit the friction contact between the dynamic seal 100 and runningsleeve 150.

The running sleeve 150 also includes a radial flange portion 150Bprovided at a second end thereof that provides a barrier for limitingaxial movement of the seal portion 108 in the leftward direction asillustrated in FIG. 8. Thus, the retaining flange 150B prevents the sealportion 108 from being dislodged from the exterior finished surface 152of running sleeve 150. The running sleeve 150 can be connected to theretainer 130 so that the seal assembly can be assembled as acassette-type seal or can be separate, as shown.

With reference to FIG. 10, a dynamic seal 200, according to theprinciples of the present invention, is shown. The dynamic seal 200 ismounted to a metal casing 202 and is also provided with a support ring204 which can be made from plastic, metal, or other materials. Thedynamic seal 200 is mounted to the casing 202 which is adapted to bedisposed in a fixed housing in a manner which is well known in the art.The dynamic seal 200 engages a rotary shaft or other member so that thedynamic seal 200 provides a sealed relationship between the rotarymember and the housing in which the casing 202 is disposed. The dynamicseal 200 includes a mounting portion 206A, 206B with the portion 206B ofthe mounting portion overlapping the metal casing 202 on at least oneface thereof. A mounting portion 206B defines a bead portion 208extending radially outward away from casing 202. The mounting portion206B can also extend radially beyond metal casing 202 so as to provide afriction engagement with the housing in which the seal assembly isinserted. The mounting portion 206A, 206B can take on many shapes andforms. The dynamic seal 200 includes an axially extending barrel portion212 extending from a radially inner end of the mounting portion 206A,206B, the axially extending barrel portion 212 is preferably generalcylindrical in shape, although other shapes, such as conical or aconvoluted curve shape, can also be utilized. The dynamic seal 200includes a radially extending portion 214 extending inwardly from adistal end 212B of the axially extending barrel portion 212. A generallyconically shaped seal portion 216 extends from a radially innermost end214A of the radially extending portion 214. The seal portion 216includes a radially inner face 218 which may be provided with aplurality of grooves 220. The grooves 220 can be helical in shape or cantake other known forms. The grooves 220 provided in the radially innersurface 218 of the seal portion 216 are capable of retaining oil thereinin order to provide lubrication between the dynamic shaft seal 200 and arotary member, and also can provide a pumping function for returningleaked oil to the oil side of the seal. A radially outer face 222 of theconically shaped seal portion 216 is provided with a stiffening bead 224defining a region of increased thickness. The stiffening bead 224 canhave different shapes, including a triangular shape, as shown, or canhave rounded or other shaped configurations. The stiffening bead of 224is provided to allow a proper contact area to develop on the sealing lip216. The bead 224 serves as an integrally formed spring for biasing thesealing lip 216 against the rotary shaft for counteracting bell mouthingof the sealing lip 216. Normally, the seal lip-free edge faces the oilside. However, reverse mounting is also possible. A dirt protective lip226 extends from the end portion 214A of radially extending leg portion214.

The support ring 204 includes an outer ring portion 204A which engagesthe bead 208 of mounting portion 206B in order to provide an axialrestrain on the support ring 204. A radially extending portion 204Bextends radially inward from the outer ring portion 204A and a secondinner ring portion 204C extends axially from an innermost end portion ofradial portion 204B. The inner ring 204C extends axially and parallel tothe axially extending barrel portion 212 of dynamic seal 200. The innerring 204C limits the radial movement of the axially extending barrelportion 212. The inner ring portion 204C includes a radially inwardlyextending leg portion 204D which is generally parallel to the radiallyextending portion 214 of the dynamic seal 200. The radially extendingleg portion 204D limits the axial movement of the radially extendingportion 214 of the dynamic seal.

The casing 202 includes an outer ring portion 202A adapted to bereceived in a bore of a housing. A first radially inward step portion202B extends radially inward from the outer ring portion 202A. Aintermediate ring portion 202C extends axially from the radiallyinwardly extending portion 202B. A mounting arm 202D extends radiallyinward from the intermediate axial portion 202C. The dynamic seal 200 ismounted to the radially inwardly extending arm 202D.

With reference to FIG. 11, a free floating support ring 300 is shown foruse with the dynamic seal 10 which is shown in FIG. 1. The support ring300 can be formed from plastic, metal, or other materials. The supportring 300 extends axially and parallel to the axially extending barrelportion 22 of the dynamic seal 10 and limits the radial movement of theaxially extending barrel portion 22. The support ring 300 includes aradially extending end surface 300 a which is generally parallel to theradially extending portion 24 of the dynamic seal 10. The radiallyextending end surface 300 a limits the axial movement of the radiallyextending portion 24 of the dynamic seal. The support ring 300 isrestrained from axial movement by radially extending portion 24 and bythe exterior housing 302, or can be otherwise restrained by othermembers such as a dust lip 38, as shown in FIG. 12, or by other meanseither attached to or separate from the seal assembly.

The description of the invention is merely exemplary in nature and,thus, variations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A dynamic seal, comprising: an annular mounting portion; an axiallyextending portion extending in a first axial direction from saidmounting portion; a radially extending portion extending radiallyinwardly from an end of said axially extending portion; a generallyconically shaped seal portion extending from an end of said radiallyextending portion in a direction opposite said first axial direction,said seal portion including a radially inner face adapted to engage arotary member and a radially outer face having a region of increasedthickness; and further comprising a running sleeve including an outersurface engaging said seal portion.
 2. The dynamic seal according toclaim 1, wherein said running sleeve includes a radial wall portionadjacent said radially extending portion for limiting axial movement ofsaid radially extending portion relative to said mounting portion. 3.The dynamic seal according to claim 1, wherein said running sleeveincludes a radial wall portion adjacent to a tip of said seal portionfor limiting axial movement of said seal portion relative to said outersurface of said running sleeve.
 4. The dynamic seal according to claim3, wherein said radially extending portion includes a protruding portionextending toward said radial wall portion of said running sleeve.